Introduction to Materials Testing and Analysis

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					                          Ferrous Metals
   Steel is the primary ferrous metal used in engineering applications.
   It is not an element; rather, it is an iron-carbon alloy that contains less than
   2% carbon.
   If the alloy contains more than 2% and less than 4% carbon, it is called
   cast iron.

Steel Production
   Steel is produced in a two-step process.
   First, iron ore is converted to pig iron in a blast furnace.
   Then, the pig iron is changed to steel in a steel-making furnace (see figure
   below).


                                Blast             Steel-
                   Iron ore   furnace Pig iron   making    Steel
                                                 furnace




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                     Ferrous Metals
                                                               Steel-
Iron ore is mined from
                                                  Scrap       making
the     ground     and                   Hot                 furnaces:
                                        gases
shipped to a steel-
                                                             •Basic
making center.                           Blast               oxygen
                            Iron ore   furnace    Fuel
                                                             •Electric
The iron ore is mixed                                        furnace
with coke, limestone,
                            Coal                  Alloys
and hot gases inside a
blast furnace.                                                           Steel

                           Limestone             Limestone
The products coming
out of the blast furnace
are pig iron, slag, and
hot gases.                 Hot gases             Iron ore


The pig iron is used to
make steel or cast iron.                Slag     Pig iron                Slag



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Ferrous Metals

         Read about these furnaces in
         Fundamentals of Materials Science
         for Technologists: by Larry Horath




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                             Ferrous Metals
Read about these furnaces in
Fundamentals of Materials Science
for Technologists: by Larry Horath




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                        Ferrous Metals
Type of Steels

   Steel is classified as either plain carbon steel, alloy steel and high-alloy
   steel.

   Plain carbon steel contains relatively few alloying elements. Therefore it is
   less expensive than alloy steel. Plain carbon steel is classified as low
   carbon steel, medium carbon steel or high carbon steel.

   Alloy steel has special qualities, such as increased strength, corrosion
   resistance, and the ability to resist wear at high temperatures. Many types
   of alloy steel exist. For example, structural steel and maraging steel.

   High-alloy steels are steels having an alloy content of 10% or higher. Two
   major families of such steels exist; stainless steels and tool steels.
   Stainless steel and tool steel are so widely used that they can be
   considered separate types of steel themselves.
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                               Ferrous Metals

                                        Steel


           Carbon              Alloy                   High-Alloy                Other
            Steel              Steel                     Steel                   Steel


 Low              Low Alloy            Maraging     Tool    Stainless   Spring       Electrical
Carbon            Structural                        Steel     Steel      Steel       Specials


  Medium                  Quench & Temper                                   Corrosion
  Carbon                     Structural                                     Resistant
                                                                            Specials

          High
         Carbon

                                          Types of Steels




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                                  Ferrous Metals
   Carbon Steel
                                             Differences
Low Carbon (Mild) Steel               Medium Carbon Steel                    High Carbon Steel
 0.05 – 0.35% Carbon       0.35 – 0.50% Carbon             0.50 – 1.00% Carbon
 Less strength             Hard and strong after heating   Hard and strong after heating
 Less hardness             More expensive than low carbon More expensive than low and
 Easy machining & forming steel                           medium carbon steels
 Least expensive
 Largest quantity produce



                                             Applications
Low Carbon (Mild) Steel               Medium Carbon Steel                    High Carbon Steel
Sheet and strip for press      Shafts;   gears;   railroad  wheels;    Forging dies; railroad rails;
work; wire and rod for nails   suspension and steering parts; intake   springs;    hammers;       saws;
                                                                                                   saws;
and     screws;    concrete    valves; overrunning clutch cam and      cylinder linings; cold chisels;
reinforcement bar; steel       hub; transmission kickdown and          forging die blocks; punchers;
plate and sections used for    reverse bands.                          shear blades; knives; axes;
structural work.                                                       screwing dies and taps; milling
                                                                       cutters; ball bearings; drills;
                                                                       wood-cutting tools; razors.
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                           Ferrous Metals
Alloy Steel

                                          Differences

     Low Alloy Structural Steel         Quench & Temper Structural           Maraging Steel
                                                  Steel
  Less alloy than other alloy steel    Stronger than low alloy structural   18 – 25% Nickel
  More alloys than carbon steel       steel                                 Low carbon content
  Less expensive than other alloy      Better properties than low alloy     Very high strength
 steel                                structural steel                      Good ductility
  More expensive than carbon           More expensive than low alloy        Good toughness
 steel                                structural steel
  Weldable                             Structural applications
  Good corrosion resistance
  Structural applications
  Alloys include:
    manganese-Silicon-Columbium-
    Vanadium-Copper




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                            Ferrous Metals
High Alloy Steels

              Stainless Steel                                  Tool Steel
   Contain enough chromium (12% min.              Applied to steels found in devices used
 required) to render them corrosion             for cutting, shearing and forming
 resistant                                      materials.
   Classified as either Ferritic, Martensitic     May be carbon or alloy steels
 or Austenitic tool steels                        0.7 – 0.9% carbon content used for
   Commonly used to meet special     special    tools subject to shock
 sanitation requirements                          1.10 – 1.30% carbon content used for
   For applications such as food                with keen cutting edges
 processing, etc                                  Drills, reamers, milling cutters, punches
                                                and dies are made from alloy tool steels
                                                  HSS are capable of making deeper cuts
                                                at higher cutting speeds whilst retaining
                                                their hardness at high temperatures
                                                  Resist softening caused by heat.




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